1. Field of the Invention
The present invention relates to railroad track inspection instruments that measure rail geometry. More particularly it relates to an apparatus for use by railroad track inspectors to determine gage, cross-level and length of track.
2. Description of the Prior Art
Railroad track inspectors have used a variety of instruments for gageing, cross-leveling and measuring the length of railroad track. Monitoring and maintaining proper rail geometry are critical tasks in preventing railroad car derailments, which often result in great economic and personal loss. A typical derailment can produce rail car cargo damage, car and engine damage, track damage, and personal injury or death. Additionally, significant collateral damage can also occur in those instances where dangerous cargo, such as explosives and toxic chemicals, are being transported.
In one recent study, it was determined that about half of all derailments were caused by the gage of the track being too wide or too narrow, while nearly a quarter were caused by cross-level and other rail-geometry problems. The occurrence of most rail-geometry problems were found to be the direct result of inadequate track inspections.
One currently used track inspection method acquires rail-geometry information with the use of an instrument that has a stick or bar that is placed on the track at the spot to be measured. The stick or bar usually includes a linear scale and a leveler. In this type of inspection, the gage and cross-level are determined only at the spot where the instrument is placed, and the leveler must be readjusted each time the instrument is moved to a new spot.
Another gage and level measuring instrument involves a device that is operated while the inspector walks along the track. A typical walking instrument includes rollers that ride on the track as the inspector manually directs the instrument. These instruments normally include a mechanical dial-type read-out that displays the gage.
Although the walking instruments have served the purpose, they have not proved entirely satisfactory under all conditions of service for a number of reasons. In many cases, considerable difficulty has been experienced due to the rollers catching in the track joints. Also, the dial-type read-outs on many of these devices are attached to the instrument at the track level, causing the reading of the dial to be difficult for the inspector to make while he is walking down the track. Also, conventional track level readers are equally hard to read for the same reason. Further, instruments that measure track length are supplied as separate equipment and are not a part of such conventional gage or level measuring instruments.
Because of these and other structural shortcomings with prior art instruments, track inspection procedures are labor intensive and costly. Many inspections are still performed with bar or stick gageing instruments. As such, routine annual track inspections are usually made only at and around turn-outs, curves and occasionally in spots where the track appears to be out of gage to the unaided eye. Also, because the procedure is slow and will not show the true and complete gage for continuous lengths of track, some areas of track are missed for long periods of time, eventually causing derailments at these locations.
Consequently, those concerned with the development of railroad inspection equipment have long recognized the need for substantial improvements in instruments that measure rail geometry. The present invention fulfills this need.